Semiclassical calculations of collision line broadening in Raman spectra of N2 and CO mixtures

We present a detailed theoretical study of pressure-broadened Raman line shapes in binary mixtures of nitrogen and carbon monoxide. The semiclassical Robert-Bonamy theory was used to calculate self-broadened Q-branch linewidths of N(2) and CO, and Lennard-Jones (LJ) potential energy surface parameters were fixed by comparing our results with extensive experimental linewidth data. For the case of N(2), the ab initio PES8 potential energy surface was investigated, however, the anisotropic repulsive part had to be reduced to ensure a good agreement with experimental linewidths. The agreement between calculations and experiments was remarkably good, both for self-broadened N(2) and CO Q-branch linewidths. Yet, our calculations were not able to predict the experimentally observed difference between Q- and S-branch linewidths of self-broadened N(2). The central results of this work are the Q-branch linewidths of N(2)-CO and CO-N(2), which have been calculated through an extrapolation of the parameters of the potential energy surfaces used for self-broadened linewidths by common combination rules.